Process for producing a water vapor impermeable board



United States Patent PROCESS FOR PRODUCING A WATER- VAPOR IMPERMEABLEBOARD Richard H. Cuhberley, Morris Township, and M. Benjamin Dell,Morristown, N. J., assignors to The Patent and Licensing Corporation,New York, N. Y., a corporation of Massachusetts Application August 26,1953, Serial No. 376,749

1 Claim. (Cl. 92-41) No Drawing.

applicator units which are used for this purpose comprise essentially ascreen-covered roll which continuously revolves in a body of bituminousemulsion, maintained in a suitable trough. A film of the emulsifiedbitumen is picked up by the screen on the roll and is transferred to thesurface of a wet fibrous ply as it passes over the applicator roll.Fresh supplies of the emulsion of the requisite consistency are passedinto'the trough as the emulsion is taken up by the roll.

Process and apparatus for coating the wet plies in this manner aredescribed, for example, in U. S. Patents Nos. 1,686,818; 1,722,432;1,724,137 and 1,732,361 and more recent improvements are found in U. S.Patents Nos. 2,622,313 and 2,622,491. This has provided a material whichis resistant to the passage of water vapor and wherein thevapor-proofing medium is inexpensively applied and substantiallyprotected from removal when the board is folded, as might be the casewith surface coated board. The bituminous material is of such a naturethat the coating between the plies does not initially prohibit the waterfrom draining off the paper, and yet after passing through drier rolls,a continuous film is formed which is resistant to the passage of watervapor.

While this process and the product thereof has been found highlysuccessful for many years, nevertheless, in certain applications such ascontainers for food, it is more desirable to have a material notpossessing the black 'color of the bitumen and having a somewhat greaterwater vapor impermeability. Furthermore, in many applications it isdesirable to have a grease barrier such as in the packaging ofdoughnuts, potato chips, etc. Such'a product should contain all of theother desirable features of the bituminous coating process, includingthe fact that the coating does not come in contact with the contents ofthe containers which may be made from the board, and also does notinterfere with the printing, folding or gluing of the board.

It is, therefore, a principal object of the present inven tion toprovide an improved paper board which is water vapor impermeable.

It is a further object of the present invention to provide an improvedpaper board which is resistant to the passage of grease. 4 I

It is a further object of the present inventionto provide a paper boardhaving a material applied between the plies thereof which is light incolor, folds without cracking, and is water vapor impermeable.

2,803,171 Patented Aug. 20, 1957 It is a further object of the presentinvention to provide an improved process for making paper board,including the application to the wet plies thereof, of a material whichforms a film in the dry board which is of a light color, resistant tothe passage of grease, folds without cracking, and is impermeable towater vapor.

These and other objects are attained by the present invention whichrelates to an improved paper board within which is a film of acomposition comprising a major proportion of wax, a minor proportion ofsolid homopolymer of isobutene, copolymer of isobutene withapproximately 2.5% of isoprene or polyethylene and mixtures thereof andclay. v

The water vapor impermeable film is put on the wet plies of the board inthe form of an emulsion, utilizing clay as the emulsifying agent,together with a cationic promoter. The clay is desirable in that itforms an emulsion which does not migrate substantially in the paper, andpermits the paper to drain before drying.

In order to obtain the desirable ratio of isobutene polymer orpolyethylene and wax to clay, it has been found necessary to utilize acationic promoter. For example, a ratio of 2 /2 parts of isobutenepolymer and wax tofl part of kaolin clay will form :an unstable emulsionwithout a promoter. However, in order to obtain ratios of 3 to 10 parts'of isobutene polymer wax per part of kaolin clay in a stable emulsion,it is necessary to use a promoter. It has been found that a cationicpromoter such as an alkyl amine is efiective.

Petroleum waxes may be used, including paraflin wax, butrnicrocrystalline wax is preferable, since it gives. a film which doesnot crack or craze easily.

The clay is selected from the group consisting of ball clay and koalinclay, but kaolin clay has been found preferable. The clay stabilizedemulsion on drying forms a film which will not flow under heat becauseof the honey-comb structure of the film. Clays such as bentonite are notdesirable because of the difliculty of drainage due to highly colloidalgels which are formed and which may permit the sheet to separate.

The isobutene polymer should be a substantially solid material which issomewhat elastomeric in nature, hav ing a molecular weight in the range30,000 to 150,000. The polyethylene should be a substantially solidresinous material, or in other words, having a molecular weight in therange 7,000 to 25,000. The invention is primarily concerned with eitherof these two materials or with mixtures thereof, or with mixtures ofeither one and small amounts of other resins. Preferably, however,substantially pure isobutene polymer is used. The most preferablematerial is GRI or butyl rubber, which is a copolymer of substantiallypure isobutene copolymerized with approximately 2.5 of isoprene. Anothersuitable commercial product is known as Vistanex, which is similar tothe butyl rubber but does not contain isoprene.

The amount of polymer should be in the range 5 to 45% of the totalpolymer wax composition, and is preferably about 25%. Mixtures of thetwo polymers found particularly suitable include 5 parts polyethylene,20 parts isobutene polymer and parts wax. In any case, a desirablecomposition of polymer and wax should have a viscosity of about 100,000centipoises at to 220 F.

The cationic promoter may be any cationic surface active agent. Ofthese, it has been found preferable to use an amine known commerciallyas Armeen H. T. D., which is approximately 25% hexadecyl amine, 70%octadecyl amine and 5% octadecenyl amine. The cationic surface activeagents are illustrated by the following:

A. Aliphatic amines and their derivatives.

Dodecylamine i alkyl alkyl I. Basic pyridinium compounds and theirsalts.

Octadecyl methylene pyridinium acetate J. Basie sulfonium, phosphoniumand antimonium compounds.

Methyl sulfate of dirnethyloctadecyl sulfonium Betaine compounds ofquaternary ammonium.

Hydrochloride of dimethyloctadecyhnethyl aminoacetateDimethylphenylbenzyl ammonium chloride. Urethanes or basic salts ofethylene diamine.

Menthol diurethane hydrochloride Polyethylene diamines and theirquaternary ammonium derivatives. 0. Polypropanol polyethanolamines.

EXAMPLE All equipment should be clean to prevent discoloration of theemulsion. The water used should be substantially free of sulfurcompounds.

Preparation of master batch Parts Polyisobutene (GRI-17) 96.5Microcrystalline wax M. P.180 F., 30 pen. at

The polyisobutene was placed in a slightly warm Banbury mixer. The batchwas mixed until the temperature rose to 250-300 F. and then about A ofthe total wax was added. This was repeated 3 times, the wax being addedonly when the temperature was between 250 and 300 F.

Preparation of emulsion Parts Master batch 150 r Microcrystalline wax236 Alkyl amine (Armeen H. T. D.) 0.2

Clay slip at 210 F.:

77.1 parts of kaolin clay (Crossman clay) 154.2 parts water Ligninsulphonate: 0.25 part of lignin sulphonate (Marasperse N) was dissolvedin 1 part of Water heated between 140 and 150 F.

Water 223 The master batch was mixed with about 45 parts wax in aBaker-Perkins dispersion mixer heated to about 100 to 120 F. When ahomogeneous blend was produced, 45 parts more of wax were added. As soonas the blend again became homogeneous, the remainder of the wax wasadded. After waiting several minutes and then raising the temperature ofthe blend to 195200 F., the alkyl amine was added. At this point themixer was stopped and the entire clay slip quickly added. The mixer wasimmediately started and the temperature maintained at 180 F. after whichthe blend inverted. After a few minutes the mixture assumed ahomogeneous appearance and part of the water at 210 F. was addedgradually for several minutes. Thereafter, the rest of the water at roomtemperature was added and the lignin sulphonate solution added. Theemulsion was passed through a 30 mesh screen and stored in polyethylenelined drums.

The emulsion of this example was diluted with equal parts of water anddelivered to an application apparatus on a paper machine of the typeadapted to apply bituminous emulsion to wet plies. The usual device forapplication is a wire covered cylinder immersed in a bath of theemulsion maintained at a constant level. The finished board made on themachine was tested after passing through the drying rolls and stacked inthe usual manner. Examination of the sheet showed that the film had notmigrated, and the plies adhered satisfactorily.

Water vapor permeability tests were made by covering weighed dishes ofanhydrous calcium chloride with samples of board, placing the dishes ina constant humidity apparatus such as the General Foods cabinet, andthen weighing the dishes again at stated time intervals. The

tests are ASTM tests D988-51T. The average water vapor transmission ofthe sheet was very low, averaging about 0.4 gram of water per 100 squareinches of board per 24 hours at 100 F. with relative humidity for 10lbs. blend per 1000 square feet of board. This com pares with a moisturevapor transmission of 2.5 grams for a coverage of about'20 lbs. per 1000square feet of bitumen.

We claim:

A process for producing a water vapor impermeable paper board comprisingapplying to a wet inner ply of the board on a cylinder machine anemulsion comprising water, a major proportion of petroleum wax, a minorproportion of a solid polymer selected from the group consisting ofhomopolymers of isobutene, copolymers of isobutene with approximately2.5% of isoprene and polyethylene and mixtures thereof, a clay selectedfrom the group consisting of kaolin and ball clay, and a cationicsurface active agent, and wherein the ratio of the combined wax andpolymer is 3 to 10 parts per part of clay, applying at least one plyover the emulsion, draining the water and drying the board in the usualmanner.

References Cited in the file of this patent UNITED STATES PATENTS Re.15,461 Perry Sept. 26, 1922 58,944 Hurlbut Oct. 16, 1866 852,918 WhiteMay 7, 1907 1,616,902 Kirschbraun Feb. 8, 1927 1,621,888 KirschbraunMar. 22, 1927 2,343,090 Smith Feb. 29, 1944 2,343,095 Smith Feb. 29,1944 2,416,447 Laughlin et a1. Feb. 25, 1947 2,487,899 Sherman Nov. 15,1949 2,492,702 Neubert et al Dec. 27, 1949 2,493,604 Walters Jan. 3,1950 2,510,661 Safiord June 6, 1950 2,563,897 Wilson et al. Aug. 14,1951 2,582,037 Hyde Jan. 8, 1952 2,610,939 Fisher Sept. 16, 19522,626,213 Novak Jan. 20, 1953 2,649,386 Snowman Aug. 18, 1953 2,658,828Pattilloch Nov. 10, 1953 FOREIGN PATENTS 178,155 Great Britain Apr. 12,1922 664,239 Great Britain Jan. 2, 1952

